Press brakes are well known in the prior art. Press brakes are most commonly used to form pans from sheet metal. Press brakes commonly have a ram which is movable up and down relative to a stationary bed. Mating dies which are mounted to the ram and bed enable sheet metal parts to be bent to a desired configuration by lowering the ram and deforming the metal between the dies. Press brakes often have a wide ram which enables multiple sets of dies to be mounted in different longitudinal locations. These different die sets perform different types of metal deformation. This enables an individual to form a pan with several different types of bends on a single press brake by moving the piece from one die set to another.
Backgages are used in conjunction with press brakes to position a part that is being formed. A backgage may include stops or "fingers" which limit how far a piece of sheet metal is extended inwardly between the bed and the ram. The backgage is positioned during tooling setup operations so that when the metal to be formed is extended through the tooling and abuts the fingers of the backgage, the desired pan configuration is achieved when the ram is lowered to form the pan. The proper positioning of a backgage is critical because incorrect positioning of the backgage results in parts that are out of tolerance and which often must be scrapped.
It is common in metal-forming operations using press brakes to have several forming operations of a similar type performed on the same part. Although some of these operations may be performed with the same tooling, it is not uncommon for the position of the fingers of the backgage to be different for each operation. In the manufacture of such parts, it is possible to have several sets of identical tooling spaced longitudinally along the ram and bed of the press brake, each of which has a different stop position. While this approach works satisfactorily, it requires multiple sets of tooling which adds expense both from an initial cost and a set-up standpoint.
An alternative approach to the manufacture of parts which require similar forming operations but different backgage positions, is the use of a movable backgage. Programmable backgage positioning devices are available from Cincinnati Inc. and others. A programmable backgage often enables an operator to perform several operations with the same tooling. The programmable backgage is programmed to move to the fingers of the backgage to the desired positions for each of the forming operations. As long as the press brake operator performs the operations in the programmed sequence, the parts will be properly formed.
A further advantage associated with the use of programmable backgages is that they greatly increase the number of forming operations that may be performed on a single press brake without having to change the setup. Die sets which perform different types of bends or forming operations may be positioned longitudinally along the ram and bed of the press brake. The operator moves the work piece from one tooling position to another as the different forming operations are performed in the sequence of part production. The backgage is programmed to move the fingers to the longitudinal position along the bed of the press brake where the operator will perform the next operation on the part. As a result the fingers are accurately and automatically positioned. Further, the movement of the fingers to a new position adjacent to a new die set serves to remind the press operator of the next operation to be performed.
While programmable backgages are very useful, they also present certain disadvantages. One common disadvantage is that when the backgage moves the fingers automatically back and forth parallel to the ram and bed, it may strike an obstruction. Such obstructions may include parts or tooling that are positioned between the prior location of the backgage and the new location to which the backgage is moving. When the backgage strikes an obstruction, damage to the backgage or the item hit will commonly occur. In the case of the backgage, the items most commonly damaged are the gage fingers which include the surfaces used to position the inward extending face of the part. When a collision occurs, the gage fingers may be bent or broken. Violent collisions may cause damage to the structure of the drive which moves the backgage. In either event, the gage fingers and perhaps other components must be replaced and the press brake must be set up again after the repairs are made. This is a very expensive process both in terms of costs to repair and machine downtime.
Programmable backgages may also be run under manual control. Manual control is used most often during set-up to determine the desired positions for the gage fingers of the backgage to achieve the desired part dimensions. Once the optimum positions are found the positions are stored in the memory of the machine. Sometimes when the machine is in the set-up mode and is being manually moved, the set-up person will inadvertently move the backgage so that the gage fingers hit an obstruction. When this occurs, damage to the gage fingers and other components are likely to result. After the repairs are made, the set-up work done prior to the collision has to be repeated.
Thus there exists a need for a backgage that reduces the risk of damage as the result of collisions between the backgage fingers and obstructions. There further exists a need for a backgage that may be readily put back in service after a collision without the need for extensive set-up activities.